MCU即微控制器（Micro Controller Unit）阶段，主要的技术发展方向是：不断扩展满足嵌入式应用时，对象系统要求的各种外围电路与接口电路，突显其对象的智能化控制能力。它所涉及的领域都与对象系统相关，因此，发展MCU的重任不可避免地落在电气、电子技术厂家。从这一角度来看，Intel逐渐淡出MCU的发展也有其客观因素。在发展MCU方面，最著名的厂家当数Philips公司。(This is based on whether a single chip computer (Microcontrollers) provides a parallel bus. The bus is provided with MCU general parallel address bus, data bus and control bus, these pins for extended parallel peripheral devices can be connected with the microcontroller through the serial port, in addition, many SCM has to the needs of the peripheral device and a peripheral interface integrated on-chip, so in many cases can not parallel expansion bus greatly reduce the packaging cost and chip size, this kind of chip called non bus mcu.)